eh, I'd keep him. potential vet visits are part of the deal and it might heal just fine.
if it's only been 2 days, it's way too early to say what he won't eat. a gecko can take a few weeks (with zero handling or extra added stress) or longer to adjust to a new home. that's probably why his red is so dark and pretty; he's stressed out.
if you do try to exchange him, you can't put them in the same cage unless they were in the same cage at the store; 2 days is enough time for any illness or parasites to be passed on. you can completely swap out the contents of the cage and do a heavy-duty disinfection and re-use it, otherwise I would never do that.